材料期刊网

PRODUCTION OF HIGHLY GRAPHITIZED MULTIWALlED CARBON ANOTUBES

X.L.Zhao1) , T.L.Guo2) , M.Ohkohchi3) , T.Okazaki3) , S.Iijima and Y.Ando3) 1) Japan Science and Technology Corporation , Department of Physics , Meijo University , Shiogamaguchi1 501 , Tempaku ku , Nagoya 468 8502 , Japan 2) Scientific Research Department , Shenyang University , Wanghuanan Street21 , Dadong District , Shenyang 110044 , China 3) Department of Physics , Meijo University , Shiogamaguchi 1 501 , Tempaku ku , Nagoya 468 8502 , Japan$

金属学报(英文版)

Multiwalled carbon nanotubes ( MWNTs) were prepared by DCarc dischargein hydrogen gas, and werethermally purified byinfrared radiation in air. The morphology of pristineand purified MWNTs was observed by scanning electron microscope ( SEM) , and the crys tallinestructureand perfection wereinvestigated by high resolution transmission electron mi croscope( HRTEM) and Raman spectrometer. Itcameto the conclusion thatthese MWNTs possessed a high degreeof graphitization and very narrow centralchannel(about1 0 nm indiameter) , giving risetotheappearanceof breathing modesfor MWNTs.

关键词: multiwalled carbon nanotubes , null , null , null , null

水热法合成N-乙酰-L-半胱氨酸稳定的Cd_xZn_（1-x）Se合金量子点

顾乐民 , 胡朗 , 姚爱华 , 王德平

功能材料

采用了N-乙酰-L-半胱氨酸为稳定剂,通过水热法制备了荧光发射峰可调、粒径均匀且结晶性能良好的ZnxCd1-xSe合金量子点,并采用紫外-可见光吸收光谱（UV-Vis）、荧光光谱（PL）、X射线衍射（XRD）、高分辨透射电镜（HRTEM）等对其结构和性能进行了表征。重点研究了Cd2＋/Zn2＋比值、初始溶液pH值、水热反应温度和时间等实验条件对ZnxCd1-xSe量子点荧光性能的影响。研究表明所制备的量子点荧光量子产率高（35%）,荧光发射谱半峰宽窄（FWHM〈50nm）,有望作为生物荧光标记物。

关键词: CdSe荧光量子点 , 水热法 , 稳定剂

Temperature dependence of elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) from first principles

Physical Review B

The temperature dependence of the elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) (x = 0.0, 0.1, and 0.2) random alloys are investigated by using the first-principles exact muffin-tin orbitals method. At 0 K, the calculated equilibrium parameters in both cubic L2(1) and nonmodulated tetragonal beta'''-Ni(2)MnGa are in good agreement with the available experimental data and other theoretical results. Separating the thermal effects into single electron excitation, volume expansion, phonon smearing, and magnetic terms, we find that phonon smearing gives the dominating positive tetragonal elastic constant (C') versus temperature (T) slope for the cubic phase. For Ni(2+x)Mn(1-x)Ga, the competition between the negative alloying effect (partial derivative C'/partial derivative x < 0) and the positive temperature effect (partial derivative C'/partial derivative T > 0) leads to nearly constant C'[x, T(M)(x)] at the martensitic transition temperature T(M)(x). For Ni(2)Mn(Ga(1-x)Al(x)), where both partial derivative C'/partial derivative x and partial derivative C'/partial derivative T are positive, however, due to the significantly decrease of T(M)(x), the critical C'[x, T(M)(x)] slightly decreases with Al doping. Furthermore, it is demonstrated that both the composition and the temperature dependence of C' are indispensable to get a reasonable theoretical T(M)(x).

关键词: shape-memory alloys;ni-mn-ga;martensitic phase-transformation;potential model;heusler alloys;ni2mnga alloy;landau theory;approximation;transitions;disorder

Magnetic and Electrical Behavior of MnTe(1-x)Sb(x) Alloys

材料科学技术（英文）

The structure, specific heat, magnetic and electrical properties of MnTe(1-x)Sb(x) (x=0, 0.1, 0.15, 0.2 and 0.25) alloys have been investigated. The MnTe(1-x)Sb(x) alloys crystallize in a hexagonal NiAs-type structure, and the impurity of MnSb phase appears when x >= 0.15. The MnTe(0.9)Sb(0.1) compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K, showing that the magnetic properties of MnTe compound are very sensitive to little compositional change. The ferromagnetism in the MnTe(1-x)Sb(x) alloys with higher Sb contents may be attributed to the impurity of MnSb phase. Energy dispersive X-ray spectroscopy analysis on the MnTe(0.9)Sb(0.1) compound indicates that Sb is very difficult to dope into the lattice of MnTe. So the anomaly of resistivity at 300 K of MnTe(0.9)Sb(0.1) and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.

关键词: Electronic transport property;Hysteresis loop;Specific heat;manganese telluride;semiconductors;ferromagnetism;scattering;exchange

L1(2)- and L1(0)-like cation-ordered structures in ZrO2-Y2O3 ceramics

Journal of Materials Research

Y0.25Zr0.75O2-x and Y0.5Zr0.5O2-y phases, with L1(2-) and L1(0-) like cation-ordered structures, respectively, have been found in ZrO2-Y2O3 ceramics in both the sintered and annealed states. High-resolution electron microscopy, energy-dispersive x-ray spectroscopy and computer simulation have been used to reveal the presence of the phases. The formation of Y0.25Zr0.75O2-x, and Y0.5Zr0.5O2-y phases was initiated during the sintering procedure and developed with the increase in annealing temperature and time. Segregation of yttrium, which was prevalent in different regions even within one grain, induced the formation of Y0.25Zr0.75O2-x and Y0.5Zr0.5O2-y phases.

关键词: yttria-stabilized zirconia;percent y2o3 alloy;x-ray-diffraction;solid-solutions;electron-diffraction;neutron-diffraction;modulated;structure;diffuse-scattering;average structure;tetragonal phase

Synthesis and Characterization of Some Transition Metal Chelates of 5-(1-Hydroxy-6-Naphthylazo-3-Sodium Sulphonate) Thiobarbituric (L1) and Barbituric (L2) Acids

Nabil S. Youssef , K.H.Hegab

材料科学技术（英文）

Some transition metal chelates of two ligands L1 and L2 were prepared and characterized by elemental analysis. The IR and 1H NMR spectra of several chelates of two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 were coordinated either in the enol or the keto form. IR spetra also showed that Fe(III)-, Ni(II)-, Mn(II)-, VO(II)-L1 and Cu(II)-L2 chelates behaved in a bidentate manner, in contrast with the two (1:1) M:L cobalt chelates with the two ligands are tridentate. TG analysis indicated the presence of three to twelve water molecules of hydration eliminated on heating up to 150°C and one or two coordinated water molecules removed at 150-180°C. The octahedral structure is proposed for all the chelates, except Cu(II)-L2 and Ni(II)-L1 chelates which have square planar geometry, based on their electronic spectra.

关键词:

Deformation and Dislocation Structure in L1_2 Titanium Trialuminide Alloys

Gengxiang HU , Shipu CHEN , Xiaohua WU , Yonghua RONG and Xiaofu CHEN(Dept. of Materials Science , Shanghai Jiao Tong University , Shanghai , 200030 , China)

材料科学技术（英文）

The deformation behaviour and the nature of dislocations of the Al3Ti-base L12 alloya modified with Fe and Mn etc, were investigated. The results show that the deformation and fracture character istics are closely related to the alloy compositions. The effect of hot-working process on the room tem perature ductility is remarkable, not only resulting in an appreciable improvement of compressive properties but also showing a 0.28% plastic strain in tensile test. The SISF dissociation of a < 110>dislocations on {111} planes was found at room temperature. The determined dissociation scheme is consistent with the mechanical behaviour of these alloys in the lower temperature region.

关键词:

First-principles study of lithium adsorption on Si(100)2 x 1 and Ge(100)2 x 1 surface at 1.0 monolayer coverage

Chemical Physics

First-principles calculations based on density functional theory have been carried out to determine the atomic structure and electronic properties of the Si(100)2 x 1-Li and Ge(100)2 x 1-Li adsorption systems at 1.0 monolayer (ML) coverage. For the Si(l 00)2 x 1-Li chemisorption system, the lowest energetic configuration is that one Li atom resides at the T3' (which is displaced along the positive y-axis from the valley bridge (T3) site by 0.90 angstrom) and the other resides at pedestal (HH) site. For the Ge(l 00)2 x 1-Li chemisorption system, the most stable configuration is found to be that one Li atom resides at HH site and the other one will penetrate deeply into the substrate surface. Chemisorption of the lithium atoms is found to result in a minimum energy configuration characterized by symmetric dimers in agreement with the results of high-resolution core-level photoelectron spectroscopy. The adsorption systems show semiconducting surface characterization. (c) 2006 Elsevier B.V. All rights reserved.

关键词: first-principles calculation;lithium adsorption;atomic structure;angle-resolved photoemission;energy electron-diffraction;core-level;spectroscopy;si(001)2x1-k surface;photoelectron-spectroscopy;alkali-metals;ab-initio;li;resolution;atoms

Relationship between bonding characteristics and mechanical properties of L1(2) intermetallics

Journal of Alloys and Compounds

The bonding characteristics of A(3)B L1(2) intermetallics have been studied by the discrete variational X(alpha) cluster method. Two concepts, i.e. similarity of bonding strength and delocalization of bonding electrons, are introduced to explain the ductility or brittleness of the materials. The analysis of bonding characteristics shows that the strength of the A-A bond is similar to that of the A-B bond in A(3)B L1(2) intermetallics, and the delocalized degree of bonding electrons is different between the ductile and brittle intermetallics. This is a dominant factor in governing the ductile/brittle behavior of the materials. Environmental embrittlement in some intermetallics is related to the reactive centers in grain boundaries, which is due to the directional bonding and a small amount of charge transfer, and the reactive centers weaken the ability against the attack of the environmental species. The effect of stoichiometry on ductility contributes to the degree of delocalized bonding electrons. Mechanical strength of the materials is correlated with the covalent bond strength.

关键词: intermetallics;mechanical properties;bond strength calculations;intergranular hydrogen embrittlement;grain-boundary strength;ll2;ordered alloys;environmental embrittlement;fracture;ductility;co3ti

承钢公司成功试炼X70、C700L两钢种

钢铁

近日，承钢公司试炼管线钢X70、卷板C700L获成功，钢坯成分、气体含量、铸坯质量等指标均达到标准要求。管线钢X70是具有高强度、高韧性和良好焊接性能的高级别管线。提钒钢轧二厂在总结以往管线钢生产经验的基础上，于4月15日对X70钢组织试制，

关键词: X70 , 钢种 , 试炼 , 管线钢 , 气体含量 , 铸坯质量 , 焊接性能 , 生产经验